How are shark pups born?

I have this trick that I use with my pregnant friends ever since I wrote this article: If they're concerned about the birthing process, I explain how shark pups are born. The process is so violent from beginning to end that delivering a 9-pound baby suddenly doesn't seem very stressful.

Take, for example, conception. Sharks don't mate in pairs, so male sharks simply bite a female shark to hold her in place while they copulate, and then they disappear. A female shark may carry several dozen embryos or eggs within her uteri, but during gestation, the ones that get teeth first tend to eat the others. And then, after gestation, a period that can last up to two years for some species, mother sharks watch as their new pups swim away as soon as they're born -- perhaps because they're trying to avoid being eaten by their mother.

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See what I mean? The next time a pregnant woman is worried about swollen feet or nighttime feedings, just remind her that at least human babies don't practice cannibalism in the womb or swim away from their mothers because they fear she's a predator.